Ducts and conduits are used to convey air in building heating, ventilation, and air conditioning (HVAC) systems. Typically the ducts in a residential building or home are arranged in a trunk and branch configuration. A plenum or trunk conveys air from an air handler of a HVAC system through various ducts and distribution boxes to smaller branch ducts that carry air to individual rooms of the home.
Many ducts, particularly trunk ducts and plenums, are formed of sheet metal and are rigid. Rigid ducts can be made from a wide variety of materials, such as, for example, sheet metal, duct board, foam board, or any other suitably rigid material. Larger ducts and distribution boxes may be formed of duct board, a rigid insulating material formed of an insulation layer and a reinforcing layer. Branch ducts may be rigid sheet metal ducts or flexible ducts. Flexible ducts are typically formed of a wire-reinforced core, an insulation layer, and an outer sheath. Ducts may terminate at duct boots that connect the ducts to air registers arranged in the floor, walls, or ceiling of a room.
These ducts and distribution boxes may be located in conditioned or unconditioned portions of the building. Leaks from connections between ducts in unconditioned spaces of a home, such as the attic, contribute to energy loss from the HVAC system because conditioned air is leaked into an unconditioned space, rather than being conveyed to the conditioned rooms of the building.
Existing methods of connecting flexible ducts to rigid ducts made of stainless or galvanized steel or duct board include sheet metal screws, mastic, adhesive tape, and plastic ties. These methods may be used on their own or in concert to connect ducts together. Mastic is a non-hardening adhesive compound that may be used on its own or with a reinforcing material such as fiberglass mesh tape.